The approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
When a router of a packet-switched network boots up, in certain approaches the router initiates border gateway protocol (BGP) sessions with BGP peers in the network. Then, the router learns routes in the network from the peers and generates routing information, such as best path information, for each BGP route based on information received from peers. The router may also generate routing information based on configuration or based on information received from other routers using a method outside BGP. The router then “advertises” the best path information to peers. The best path information that is sent may be called an update message. Prior to receiving advertised routes, a peer may be configured. Configuring peers and advertising a set of updates to multiple peers may occupy valuable resources, may require a great deal of messages to be formatted, and may be considered a costly overhead. This overhead slows convergence time as the number of peers on a BGP router increases. “Convergence” is the process by which all peers acquire complete and consistent route information.
BGP update messages may be grouped together into peer groups based on configuration, and update messages may be sent to the whole group. Grouping update messages together based on peer-group configuration may reduce the amount of system processing resources needed to generate updates for a routing table. This method, however, has the following limitations:                All peers that share the same peer-group configuration must share the same outbound routing policies and session characteristics; and        Even if peers in different peer groups have the same outbound policy, they cannot share update messages. The update messages for each peer group are generated/formatted independently.        
As a result of these limitations, network operators often configure smaller peer-groups. This reduces the efficiency of update message processing. It would be useful to overcome the aforementioned overhead problems and limitations.